First described in 1965, sleep apnea is a breathing disorder characterized by brief interruptions (10 seconds or more) of breathing during sleep. Sleep apnea is a common but serious, potentially life-threatening condition, affecting as many as 18 million Americans.
There are two types of sleep apnea: central and obstructive. Central sleep apnea, which is relatively rare, occurs when the brain fails to send the appropriate signals to the breathing muscles to initiate respirations, e.g., as a result of brain stem injury or damage. Mechanical ventilation is the only treatment available to ensure continued breathing.
Obstructive sleep apnea (OSA) is far more common. Normally, the muscles of the upper part of the throat keep the airway open to permit air flow into the lungs. When the muscles of the soft palate at the base of the tongue and the uvula (the small fleshy tissue hanging from the center of the back of the throat) relax and sag, the relaxed tissues may vibrate as air flows past the tissues during breathing, resulting in snoring. Snoring affects about half of men and 25 percent of women—most of whom are age 50 or older.
In more serious cases, the airway becomes blocked, making breathing labored and noisy, or even stopping it altogether. In a given night, the number of involuntary breathing pauses or “apneic events” may be as high as 20 to 30 or more per hour. These breathing pauses are almost always accompanied by snoring between apnea episodes, although not everyone who snores has this condition. Sleep apnea can also be characterized by choking sensations.
Lack of air intake into the lungs results in lower levels of oxygen and increased levels of carbon dioxide in the blood. The altered levels of oxygen and carbon dioxide alert the brain to resume breathing and cause arousal. The frequent interruptions of deep, restorative sleep often lead to early morning headaches, excessive daytime sleepiness, depression, irritability, and learning and memory difficulties.
The medical community has become aware of the increased incidence of heart attacks, hypertension and strokes in people with moderate or severe obstructive sleep apnea. It is estimated that up to 50 percent of sleep apnea patients have high blood pressure.
Upon an apneic event, the sleeping person is unable to continue normal respiratory function and the level of oxygen saturation in the blood is reduced. The brain will sense the condition and cause the sleeper to struggle and gasp for air. Breathing will then resume, often followed by continued apneic events. There are potentially damaging effects to the heart and blood vessels due to abrupt compensatory swings in blood pressure. Upon each event, the sleeping person will be partially aroused from sleep, resulting in a greatly reduced quality of sleep and associated daytime fatigue.
Although some apneic events are normal in all persons and mammals, the frequency of blockages will determine the seriousness of the disease and opportunity for health damage. When the incidence of blockage is frequent, corrective action should be taken.
The common method of diagnosing and determining the severity of sleep apnea is polysomnography. Polysomnography is a test that records a variety of body functions during sleep, such as the electrical activity of the brain, eye movement, heart rate, etc.
There are several methods and devices presently available for the treatment of snoring and OSA. There are oral appliances which are designed to displace the mandible (lower jaw) in an anterior (forward) direction by attaching to the upper and lower teeth. The intent is to displace the tongue in an anterior direction, increasing the size of the opening behind the tongue, resulting in an increased airway cross section. These devices have been only partially successful and are not tolerated by a significant percentage of the patients who have them fitted.
Another means of controlling snoring and sleep apnea is the use of a machine that delivers increased air pressure to the nose and mouth of the sleeper. These machines are described as CPAP (Continuous Positive Airway Pressure) machines. They entail wearing of a mask, headgear, and flexible hose which is attached to the air pump. A continuous flow of air at higher than ambient air pressure is forced into the persons' airway, preventing closure of the soft tissue and the resultant apneic event. These devices have also been shown to reduce snoring but not necessarily prevent snoring entirely.
Although effective, the CPAP machine is not widely accepted by the patients. Discomfort, the sound of the air pump, claustrophobia and the stigma of being seen while wearing the mask, headgear, and hose have all been listed as reasons for not continuing use of the CPAP.
Several surgical approaches are used for these afflictions. One is a uvulopalatopharyngoplasty (UPPP) in which tissue at the posterior portion of the soft palate is removed, either by surgical excision or by use of a laser (so-called laser ablation). This is an invasive surgical procedure involving considerable pain in the recovery period, which can be lengthy. Side effects can involve escape of fluids upward into the nasal cavity and increased incidence of bothersome choking events. The long-term success of the UPPP in curing snoring and especially sleep apnea is only approximately 50%.
Other even more involved and invasive surgeries involve tongue reduction in which a section of the tongue is excised to reduce the tongue volume and maxillomandibular advancement in which the upper and lower jaws are severed and repositioned to create increased airway space will improve upon the UPPP success rates. Even more so than the UPPP, these procedures are painful, costly and require long recuperative periods. Absolute assurance of a successful outcome is lacking in these operations, also.
An office-based procedure—called the Somnoplasty® procedure (developed by Somnus Medical Technologies) can be performed using local anesthesia to treat upper-airway obstructions. The procedure uses controlled, low-power radiofrequency energy to create one or several submucosal volumetric lesions in the soft palate. Over a period of 6 to 8 weeks, the lesions are naturally resorbed, reducing tissue volume and stiffening remaining tissue in the desired area.
Other more intrusive treatments such as surgical interventions, i.e. glossectomy (reduction of the size of the tongue 34), genioglossal advancement (pulling the genioglossus muscle in an anterior direction to bring the tongue forward), maxillomandibular advancement (surgical alteration of a portion of the jaw bone and teeth plus the portion of the skull to which the upper teeth are attached) and uvulopalatopharyngoplasty—UPPP (the removal of a portion of the soft palate, either by surgical resection or laser ablation) all permanently modify the anatomy and can affect swallowing, speech and comfort in a negative manner. Other proposed devices, such as implantation of springs and other stiffening devices, can also have an undesired effect on daytime functions.
The need remains for simple, cost-effective devices and methods for reducing or preventing snoring and obstructive sleep apnea.